Security Resilience

CVE-2026-100635

Public PoC
Published
26 September 2026
Modified
08 October 2026
CVSS Score v4 8.2
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0026 16th percentile
Risk Priority 42 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-100635 is a high-severity Cleartext Transmission of Sensitive Information (CWE-319) vulnerability. Its CVSS base score is 8.2 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Network Sniffing (T1040); ranked at the 16th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SC-8 (Transmission Confidentiality and Integrity) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A04:2025 Cryptographic Failures

EU & UK References

Vulnerability Data

SiYuan before v3.8.4 contains an authentication bypass vulnerability in the publish service where session cookies are issued without Secure or SameSite attributes over plaintext HTTP connections. An on-path attacker can observe a valid publish-visitor-session-id cookie from a Basic Auth exchange…

more

and replay it to access authenticated publish endpoints without knowing the account password.

CWE(s)
CWE-319

Related Threats

MITRE ATT&CK Enterprise Techniques

T1040 Network Sniffing Credential Access
Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-11946Shared CWE-319
CVE-2025-63364Shared CWE-319
CVE-2024-37183Shared CWE-319
CVE-2024-26288Shared CWE-319
CVE-2023-32784Shared CWE-319
CVE-2025-5270Shared CWE-319
CVE-2025-23060Shared CWE-319
CVE-2023-34441Shared CWE-319
CVE-2024-35495Shared CWE-319
CVE-2025-13490Shared CWE-319

Affected Assets

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SC-8 Transmission Confidentiality and Integrity partial match

SC-8 directly requires protecting confidentiality of transmitted information, which structurally eliminates cleartext transmission of sensitive data.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.DS-02 full match
blocks

Encryption of data-in-transit directly prevents cleartext transmission while the control also addresses integrity and availability.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.17 Authentication information mostly match
removes
A.8.21 Security of network services mostly match
blocks

A.8.21 mandates identifying/implementing network service security features (explicitly including encryption and connection controls), formulating rules that cover authentication/authorization/monitoring/VPNs, and ensuring providers do the same; this stops cleartext transmission from being exploitable in the large majority of network channels, with a bounded remainder (e.g. internal non-networked flows or unaddressed legacy protocols).

A.5.14 Information transfer partial match
blocks

Mandating cryptographic protection and stronger authentication on public networks stops the transmission of plaintext sensitive information.

A.8.5 Secure authentication partial match
removes

References